Special Seminar: Controlling Electron-Phonon Coupling in Functional Electronic Materials

 In the prevailing picture of charge and exciton transport in functional electronic materials, phonons and molecular vibrations are thought to cause scattering and localisation of electronic wavefunctions. This results in the suppression of exciton and charge transport, leading to poor mobilities and diffusion lengths. This also accelerates non-radiative decay dynamics and widens PL linewidths. Since phonons and molecular vibrations are inherent to the structure of materials, this problems has long been thought to be unavoidable.

In this talk I will present recent experimental ultrafast spectroscopy and ultrafast microscopy results which suggest that we overcome this seemingly unavoidable problem. Starting with molecular systems, I will discuss a new mechanism for exciton diffusion, transient delocalisation, which can enable exciton diffusion constants up to 1cm²/s and diffusion lengths greater than 300nm. I will also discuss results which suggest that it is possible to completely decouple excitons from high-frequency vibrational modes, thus greatly supressing non-radiative recombination and enabling high luminescence efficiencies in low-bandgap molecular systems with narrow linewidths. This may have important implications for both optoelectronic materials and bio-imaging/assays. Finally, I will discuss how we might transfer what we have learned from molecular systems to inorganic materials such as those used in batteries, to enable new routes to faster ion diffusion in these systems.